1. Field of the Invention
This invention relates to a method for manufacturing a copper-clad laminate with ultra-thin copper films.
2. Description of the Related Art
Copper-clad laminates are used in the production of printed circuit boards. It is desirable to use relatively thin copper foils (less than 16 microns) on the copper-clad laminates for the production of printed circuit boards with compact and highly integrated circuit patterns thereon due to drawbacks, such as side etching effect during etching process for the formation of circuit lines on the printed circuit boards, and time consuming and undesirable enlargement of through-holes during the process of the formation of the through-holes in the printed circuit boards via laser beam, which are consequences of using thick copper foils in the processing of the printed circuit boards. However, conventionally, copper foils are made by electrodeposition techniques and are hard to produce with the desired thickness without formation of pinholes. Moreover, even if such thin copper foils can be produced, they are difficult to store and transport, and are susceptible to folding when laminated with a substrate (which is generally called a prepreg that is in the form of a fabric sheet coated with curable epoxy resin or a glass-fiber reinforced curable epoxy resin sheet) during a hot pressing step. A conventional process for the production of printed circuit boards involves forming relatively thick copper foils on a glass-fiber reinforced epoxy resin substrate and subsequently etching the copper foils to achieve the desired thickness. As a consequence, the process induces environmental problems and results in uneven surfaces for the copper foils.
Therefore, the object of the present invention is to provide a method for manufacturing a copper-clad laminate with ultra-thin copper films that is capable of overcoming the aforementioned drawbacks.
According to the present invention, a method for manufacturing a copper-clad laminate comprises the steps of: preparing rigid plate-shaped first and second carriers having first and second flat surfaces, respectively; forming first and second thin metal films on the first and second flat surfaces of the first and second carriers, respectively; forming ultra-thin first and second copper films on the first and second thin metal films, respectively, via electroplating techniques; coating curable first and second resin layers on the first and second copper films, respectively; heating the first and second resin layers so as to form hardened first and second semi-cured resin layers on the first and second copper films, respectively; stacking a first assembly of the first carrier, the first thin metal film, the first copper film, and the first semi-cured resin layer on a second assembly of the second carrier, the second thin metal film, the second copper film, and the second semi-cured resin layer in a manner that the first and second semi-cured resin layers are brought into contact; hot pressing the first and second assemblies so as to completely cure and integrate the first and second semi-cured resin layers to form a cured resin body that is bonded to and that cooperates with the first and second copper films of the first and second assemblies to form a laminated body; and removing the first and second carriers together with the first and second thin metal films from the laminated body.